This invention relates to ophthalmoscopic instruments, and more particularly to a wide angle achromatic photographic objective for use in such ophthalmoscopic instruments.
In conventional ophthalmoscopes and eye-fundus cameras, a large proportion of the objectives are formed as a positive meniscus lens convex toward an object (human eye). With this type objective, however, the angle of view has to be limited to about 30 degrees or less, or otherwise a substantially lowered picture quality will be resulted.
To increase the angle of view up to about 45 degrees, the objective preferably takes a biconvex form. When a chromatic correction is required, the biconvex objective is generally designed to have a cemented surface or surfaces. This gives rise to introduction of disturbing reflections from the cemented surface or surfaces.